1. Field of the Invention
The present invention relates to a throttle valve control apparatus and to a throttle valve control method for an internal combustion engine, wherein a throttle valve is opened and closed by an actuator.
2. Description of Related Art
In a vehicle control apparatus described in, for example, Japanese Patent Application Laid-Open No. 10-299546, a throttle valve is opened and closed by an actuator. In this apparatus, a target throttle opening amount is set based on the accelerator operation amount and the revolution speed of an internal combustion engine. The degree of opening of the throttle valve is controlled so as to become equal to the target throttle opening amount. Furthermore, based on the position of the throttle valve in the opening/closing direction, the apparatus determines whether the engine is idling. If the engine is in the idle state, the apparatus substantially fixes the throttle valve in position, thereby stabilizing the revolution speed of the engine in the idle state.
In the apparatus described above, however, if the accelerator is depressed, even if depressed slightly, during the idle state, the throttle valve is opened, that is, the throttle valve is shifted away from a completely closed position. As a result, the apparatus determines that the engine is not in the idle state. Once it is determined that the engine is not in the idle state, the apparatus increases the target throttle opening amount with increases in the engine revolution speed, so that the throttle valve is further opened and, therefore, the engine revolution speed further increases. If the load on the engine is small in this situation, the throttle valve is gradually opened so that the engine revolution speed greatly increases, thus discomforting a driver of the vehicle.